Down-hole tool hydraulic force intensifier

ABSTRACT

A down-hole tool hydraulic force intensifier is disclosed utilizing an intensifier piston having an enlarged fluid facing top surface for receipt of hydraulic pressure thereon to force such intensifier piston against the activating structure of the down-hole tool to effectively increase the hydraulic force thereon.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to apparatus for increasing the force usedto activate a hydraulically operated down-hole tool and moreparticularly relates to an apparatus that increases such force withouthaving to increase the pressure of the hydraulic fluid.

[0003] 2. History of the Prior Art

[0004] It is conventional practice when drilling well boreholes tocreate such boreholes in steps. Initially a large diameter borehole isdrilled to a particular depth. In order to structurally support theborehole and prevent collapse, the borehole is lined with standard steeltubing known as a casing which is cemented in place. Subsequent sectionsof the borehole are then drilled with a smaller drill bit attached to awork string which can be lowered through the previously installedcasing. As a consequence each section of the borehole and casing willhave a smaller diameter to that which is above it.

[0005] Expandable reaming tools are commonly used during the abovedescribed procedure and typically comprise a plurality of expandablearms which can move between a closed and an open position. Theexpandable reaming tool is passed through the in-place casing with thearms in a closed position behind a pilot drill bit which drills thesection of the borehole. After passing through the casing the expandablereaming tool or underreamer can be opened in order to enlarge theborehole below the casing.

[0006] The blades of extendible reaming tools are commonly extended by apiston which is activated by a hydraulic force created by the pressureof fluid passing through the work string. However it will be appreciatedthat boreholes often extend several thousands of meters in depth, and itis therefore difficult when working at such depths to effectivelycontrol the pressure of the hydraulic fluid and hence the driving forceon the tool. Fluid pressure is typically determined by pumping apparatusat the surface, and such pressure may progressively diminish due tovarious back pressures at remote distances down-hole. It is also notalways desirable, or possible, to use high pressure in certainconditions, for example, in deep, low-pressure wells.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a tool designof the type which is activated by a hydraulic force, the level of whichforce is adjustable without the requirement of an increase in fluidpressure beyond a predetermined maximum.

[0008] It is therefore an object of this invention to provide anapparatus for increasing the hydraulic force applied to a hydraulicallyoperated down-hole tool for any given hydraulic fluid pressure.

[0009] According to the present invention there is provided ahydraulically operated down-hole tool, the tool having one or morepistons in series wherein each piston provides a fluid facing surface onwhich hydraulic fluid operates wherein the combined fluid facing surfaceof the plurality of pistons increases the surface area on which thehydraulic fluid operates such that the force exerted by the hydraulicfluid on the down-hole tool is proportionately greater than the forcewhich would be produced by any given hydraulic pressure alone.

[0010] In a preferred embodiment the down-hole tool of this inventioncan be an expandable reaming tool having a plurality of reaming memberswhich are movable between a first closed position and a second expandedposition. The reaming members can be moved from a first closed positionto the second expanded position by virtue of the movement of a firstactivating piston. Such activating piston is usually biased againstmovement under hydraulic force by a mechanical spring. The spring canserve to return the activating piston to its original position whenfluid pressure is reduced. The expandable reamer tool can have aplurality of restricted exit flow ports.

[0011] An intensifier piston or pistons in series of this invention isused in conjunction with such activating piston. Such intensifierpiston(s) is adapted to be acted upon by fluid pressure and ismechanically linked with the activating piston so as to transmit suchforce onto the activating piston. A plurality of intensifier pistons inseries can be used to increase the total surface area upon whichpressurized fluid is able to act, thereby increasing the totalactivating force.

[0012] The activating and intensifier piston(s) can have an internalcollinear axial bore. The intensifier piston can have a plurality offluid outlet ports which allow fluid to pass from the internal bore ofthe intensifier piston into a recess located substantially behind theactivator piston. The intensifier piston can be slidably mounted in asub wherein the sub is connectable to a work string.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates a longitudinal cross-sectional view of theintensifier piston of this invention.

[0014]FIG. 2 illustrates a longitudinal cross-sectional view of anintensifier sub without an associated intensifier piston therein.

[0015]FIG. 3 illustrates a longitudinal cross-sectional view of theintensifier piston of FIG. 1 in position within the sub of FIG. 2.

[0016]FIG. 4 illustrates a longitudinal cross-sectional view of adown-hole tool having an activator piston and intensifier pistontherein.

[0017]FIG. 5 illustrates the down-hole tool of FIG. 4 after hydraulicpressure has been applied thereto.

[0018]FIG. 6 illustrates a longitudinal cross-sectional view of analternate embodiment of this invention having two intensifier pistonsarranged in series.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0019]FIG. 1 illustrates intensifier piston 1 having narrow piston body2 and relatively narrower throughbore 3. Piston body 2 has a pluralityof drilled holes 4 defined therein. Piston body 2 is designed such thatit provides an enlarged fluid facing top surface 5 on which hydraulicfluid can operate to create a downward force. Body 2 also has an O-ringseal 6.

[0020]FIG. 2 illustrates an intensifier sub 7 having O-ring 8 and subthrough holes 9 which act as pressure equalizers. Sub 7 further has athreaded end connection 10 which enables sub 7 to be mounted on a workstring or the like. The relationship between sub 7 of FIG. 2 andintensifier piston 1 of FIG. 1 is shown in more detail in FIG. 3. InFIG. 3 it can be seen that intensifier piston 1 is slidably fittedwithin sub 7 and can move relative to sub 7 under the influence ofhydraulic fluid operating on fluid facing top surface 5.

[0021] In FIGS. 4 and 5 a down-hole tool 11 is depicted. Shown in FIGS.4 and 5 is an extendible reaming tool otherwise known as an underreameralthough it should be noted that any hydraulically operated tool can beused and still fall within the scope of the present invention. Tool 11comprises body 12 and plurality of blades 13 which can be moved from afirst closed position, as seen in FIG. 4, to a second open position, asseen in FIG. 5 where the blades have been rotated 90 degrees. In use,the tool is run into a well borehole with blades 13 entering first. Body12 contains activating piston 14 which is movable and which acts toextend blades 13. The main body of the tool also comprises an activatingmember 15 which is located next to coiled spring 16.

[0022] To activate the underreamer, hydraulic fluid is pumped throughthe work string which, although not shown, is well known in the priorart. Positioned directly behind activating piston 14, and in seriestherewith, is intensifier piston 17 and associated piston sub 18.Intensifier piston 17 increases the force exerted on activating piston14 by hydraulic fluid by virtue of increasing the surface area on whichthe hydraulic fluid operates. Specifically, the hydraulic fluid pumpedfrom the surface of the well borehole will push on fluid facing surfaces19 and 20 and cause intensifier piston 17 to move relative to piston sub18 from the position illustrated in FIG. 4 to the position illustratedin FIG. 5. In turn, activating member 15 and coiled spring 16 arecompressed, moving activating piston 14 in a downward direction andmoving blades 13 from the closed position shown in FIG. 4 to the openposition shown in FIG. 5 where the blades are shown rotated 90 degrees.

[0023] Intensifier piston 17 also has defined therein intensifier pistonbore 21. It will be appreciated that fluid will be able to pass throughintensifier piston bore 21 through intensifier piston 17. This fluidflow passes through intensifier piston bore 21 until it reaches drilledpiston holes 4, as shown in FIG. 1. The fluid can pass through theseholes 4 into a recess 22 which is located next to, and directly above,activating member 15. This fluid acts to create further force onactivating member 15 of activating piston 14 which in turn helpscompress coiled spring 16 and move activating piston 14 downwards.Activating piston 14 also has an activating piston bore 23 definedtherein.

[0024] It will be appreciated that the advantage of the presentinvention lies in the fact that the inclusion of the intensifier pistonincreases the surface area on which the hydraulic fluid within the workstring can push, and consequently creates an increase in force on theactivating piston which activates the hydraulic tool. This increasedforce can be achieved without increasing the pressure at which the fluidis pumped down-hole.

[0025]FIG. 5 illustrates the piston when activated. Fluid can escape bymeans of a plurality of restricted exit ports, not shown, on theunderreamer tool itself, or by being forced back through activatingpiston 23 of activating piston 14 via back pressure and exiting intorecess 22.

[0026]FIG. 6 illustrates an alternate embodiment of the presentinvention wherein a double intensifier piston is used. Sub 24 iselongated such that a first and second intensifier piston 25 and 26 arepositioned in series and are aligned with one another directly behind anactivator piston which is not shown. It will be appreciated that theinclusion of two intensifier pistons will further increase the surfacearea on which the hydraulic fluid can operate, namely on fluid facingsurfaces 27, 28, 29 and 30. Although only one or two intensifier pistonsare illustrated, it is within the scope of this invention that a seriesof such intensifier pistons can be incorporated into a tool.

[0027] Although the present invention has been described with referenceto particular embodiments, it will be apparent to those skilled in theart that variations and modifications can be substituted thereforwithout departing from the principles and spirit of the invention.

I claim:
 1. A hydraulic force intensifier for use with a down-hole toolhaving activating means and a bottom, comprising: an intensifier pistonhaving an enlarged fluid facing top surface, a narrow piston body and arelatively narrower throughbore defined longitudinally therein; a subhaving an aperture defined therein for slideable receipt of said pistonbody and enlarged fluid facing top surface of said intensifier piston,said sub including means for attachment to said down-hole tool at thebottom thereof; means for attachment to a source of hydraulic pressuredfluid; and said enlarged fluid facing top surface adapted to receivesaid hydraulic fluid pressure over a wider surface area than wouldotherwise be received by said tool for increasing the force of saidintensifier piston body on said activating means of said tool.
 2. Theforce intensifier of claim 1 further including: a plurality of saidintensifier pistons aligned in series to receive said hydraulic fluidpressure against the enlarged fluid facing top surfaces of each of saidintensifier pistons for effectively increasing the pressure on saidactivating means of said down-hole tool.